This invention relates to axially movable members, and in particular to valves and in particular nozzle-style check valves.
In a conventional nozzle-style check valve, valve closure is spring assisted. When the flow decelerates the springs pushes a circular disk into the valve seat preventing reverse flow and valve slam. Normal flow pushes the disc backwards and fully opens the valve. In this type of design, flow accelerates in the seat area around the valve seat, enabling valve opening while locally lowering the static pressure. The annular diffuser is subsequently used to gradually recover this pressure with minimum losses.
The circular disk is mounted on a shaft, which in turn is mounted in a bearing or bearings. These bearings are mounted in the shaft guidance. The bearings permit the axial movement of the disk, while limiting lateral disk movement. The disk will therefore align with the valve seat and seal properly when closing. An axial compression spring assists in closing the valve.
Disadvantages with this conventional check valve include bearing friction (which increases due to contamination), reducing the effective spring force and decreasing the valve""s dynamic response, the length of the valve body necessary to house the shaft and bearings, and cost of the shaft-bearing-shaft guidance assembly.
This invention seeks to overcome problems with the prior art.
Therefore, according to a first aspect of the invention, there is provided a valve, comprising a valve body defining a fluid passageway, with a valve seat in the fluid passageway, a valve disk support mounted within the valve body, a front flexure plate mounted on the valve disk support, a valve disk secured to the front flexure plate and disposed within the valve body, the valve disk having a front side and a back side, the valve disk being movable axially within the valve body, the valve being closed when the front side of the valve disk contacts the valve seat, and the front flexure plate being axially extendable to accommodate axial valve disk movement while limiting lateral valve disk movements.
According to a further aspect of the invention, there is provided an assembly for supporting an axially movable member, in which the axially movable member is supported by front and back flexure plates, and the front and back flexure plates are spaced such that each is axially extended when the other is flat.
According to a further aspect of the invention, there is provided an assembly for supporting an axially movable member, the assembly comprising a housing defining a passageway, a support mounted within the housing, a flexure plate mounted on the support, an axially movable member secured to the front flexure plate and disposed within the housing, A compression spring mounted between the support and the axially movable member to bias the axially movable member in one axial direction, and the flexure plate being axially extendable to accommodate axial movement of the axially movable member while limiting lateral movement of the axially movable member.
The flexure plates are preferably flat axial springs fabricated by machining spiral cuts in flat, circular or annular plates. The flexure plates permit the required axial movement of the valve disk, while sufficiently restricting lateral valve disk movement. Their operation is frictionless and they are less expensive to produce than a shaft, bearings and shaft guidance.
In a further aspect of the invention, different numbers of flexure plates can be used in front and back locations by stacking the flexure plates. Adding more flexure plates will increase the lateral stiffness, as would be required for a heavy valve disk. The number of flexure plates will also affect the axial stiffness and thus the rating of the required compression spring. Changing the number and shape of the spiral cuts can vary the flexure plates"" properties.
The configuration of the flexure plates can be adjusted by changing the length of the inner spacer rods relative to the outer spacer rods, which fix the axial distance between the front and back flexure plates. Adjusting the configuration can also be a means of sizing the axial stiffness of the flexure plate assembly and compression spring to achieve a wide variety of effective spring stiffnesses as required for varying valve opening and closing conditions, i.e. the valve""s dynamic response. The wide available range of closure forces result in a valve with faster dynamic response than in the prior art.
These configurations allow the design of a short, hence more compact, valve body with a lower non-dimensional pressure loss coefficient than prior art, typically 0.85.
In a further aspect of the invention, depending on the particular flow conditions, the flexure plates provide sufficient closure force and an axial compression spring is unnecessary.
These and other aspects of the invention are described in the detailed description of the invention and claimed in the claims that follow.